Fluid proportioning system

ABSTRACT

A plurality of cylinder and piston assemblies for connection on their inlet sides to respective fluid sources and on their outlet sides to a common vessel, the cylinder-and-piston assemblies each including valve means operable to communicate a selected side of the respective piston with one of the associated supply fluid and common vessel, and communicate the other piston side with the other of the supply fluid and common vessel, the valve means being interconnected for operation in predetermined relation.

United States Patent Tanner 1 Apr. 4, 1972 54] FLUID PROPORTIONINGSYSTEM 3,487,980 1/1970 Tanner ..222/250 [72] Inventor: Dale Tanner 21Academy Avenue, wood 3,224,642 12/1965 Martelaere ..222/250 X buryHelghts 08096 Primary Examiner-Robert B. Reeves [22] Filed: Feb. 24,1970 Assistant Examiner-Thomas E. Kocovsky I pp 13 528 Attorney-RobertK. Youtie [57] ABSTRACT [52] U.S. CI. ..222/6l, 222/71, 222222//235305,A plurality of cylinder and piston assemblies for connection 5 I l t UGo] f "/44 on their inlet sides to respective fluid sources and on theirouti d 61 7 let sides to a common vessel, the cylinder-and-piston assem-I e 0 care 129 4 'blies' each including valve means operable tocommunicate a selected side of the respective piston with one of theassociated supply fluid and common vessel, and communicate [56] Rem-anusCited the other piston side with the other of the supply fluid andUNITED STATES PATENTS common vessel, the valve means beinginterconnected for 3 033 218 5/1962 C 222/249 X operation inpredetermined relation.

a en 2,536,299 1 /1951 Martin ..222/249 X 5 Claims, 7 Drawing Figures 5I 7 J4 {175p I;

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s & e 4/ l\ \X I PATENTEBAPR 4 m2 sum 10 3 VQ I w %M\ A i N wry/me R E NN I m f A I. w w r B V QM ATTO/P/IFX PATENTED APR 4 I972 SHEET 2 BF 3DALE 3) PATEHTEUAPR 4 m2 SHEET 3 OF 3 KMZK FLUID PROPORTIONING SYSTEMBACKGROUND OF THE INVENTION In the proportioning, mixing or blending offluids, there have heretofore been problems in controlling the accuracyor precision of proportioning, this usually requiring accurate speedcontrol of several pumps. In addition to the problems of pump control,these prior systems were relatively expensive, both initially andsubsequently, requiring investment in a plurality of pumps, drive meanstherefor, pump controls, fittings and connections, as well as regularmaintenance and replacement parts.

SUMMARY OF THE INVENTION Accordingly, it is an important object of thepresent invention to provide a fluid proportioning system for thecontinuous mixing or blending of separate fluids which eliminates theneed for individual pumps for each fluid, to thereby considerably reducethe necessary capital expenditure for such a system, as well aseliminating considerable auxiliary equipment and the cost thereof, togreatly simplify the instant system and assure high reliability inoperation throughout a long useful life with a minimum of maintenanceand repair.

It is still another object of the present invention to provide a fluidproportioning system of the type described wherein a plurality ofmetering devices are operable in response to differential pressures ofthe fluids involved, and operatively associated with each other toassure a predetermined proportionate metering by the respective meteringdevices of their associated fluids.

It is still another object of the present invention to provide a fluidproportioning system having the advantageous characteristics mentionedin the preceding paragraphs wherein the relative proportions metered bythe respective metering devices is readily adjustable within a widerange for a great degree of versatility in use.

Other objects of the present invention will become apparent upon readingthe following specification and referring to the accompanying drawings,which form a material part of this disclosure.

The invention accordingly consists in the features of construction,combinations of elements, and arrangements of parts, which will beexemplified in the construction hereinafter described and of which thescope will be indicated by the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective viewillustrating a fluid proportioning system in accordance with theteachings of the present invention.

FIG. 2 is a sectional elevational view taken generally along the line2-2 of FIG. 1.

FIG. 3 is a partial horizontal sectional view taken generally along theline 33 of FIG. 1.

FIG. 4 is a partial horizontal sectional view taken generally along theline 44 of FIG. 2.

FIG. 5 is a partial sectional view similar to FIG. 4, but illustratingan alternate condition of operation.

FIG. 6 is a schematic representation of electrical circuitry of thepresent invention.

FIG. 7 is a diagrammatic representation of the electrical circuitry ofFIG. 6 in association with an actuating mechanism.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now more particularlyto the drawings, and specifically to FIG. 1 thereof, a proportioningsystem is there merge into a single conduit 24 and pass therefrom to apump 25. The pump 25 may discharge say to a vessel 26, for further useor dispensing of the blended fluid, as will appear more fullyhereinafter.

The overall fluid proportioning system, as shown in FIG. 1, may utilizemetering devices 11-14 similar to that disclosed in my prior US. Pat.No. 3,487,980. Further, the metering devices 1 1-14 may each besubstantially identical, and may be of the same dimensions or dimensionsdiffering from each other, as illustrated in FIG. 1. However, as willappear more fully hereinafter, the several metering devices 11-14 areeach individually adjustable for achieving the desired proportions offluids.

The metering device 11 is shown in detail in FIG. 2, one such showingbeing sufficient, as the several metering devices 11-14 may all beidentical. The metering devices 11-14 may all rest in upstandingrelation on a hollow platform or base 30. The metering device 11includes a generally vertically disposed open ended tubular casing orcylinder 31. The lower end of the cylinder or casing 31 is effectivelyclosed by seating on the hollow platform or base 30, and is furtherprovided in its lower end with a bearing 32. The upper end of thecylinder or casing 31 may be closed by a cover or plug 33. The meteringdevice 11 may be secured in position on the hollow base 30 by anysuitable means, such as elongate tie members or hold-down rods 34 eachextending from the upper end closure or plug 33 to and through the upperwall of hollow base 30. A wing nut 35, or other suitable means may bedetachably secured to each hold-down 34, to removably retain therespective metering assembly in position. I

The cylinder or casing 31 of metering device 1 1 is provided in itslower region with an inlet or through fitting 37 for connection in fluidcommunication with the inlet or supply conduit 15. The several meteringdevices 12-14 are similarly provided with inlets or fittings forconnection to respective inlet conduits 16, 17 and 18. The inlet 37 islocated in a lower region of the casing 31, adjacent to and spaced abovethe base 30.

In substantially the same horizontal plane as the inlet 37, the cylinderor casing 31 is further provided with an outlet or through fitting 38for connectionin fluid communication with the conduit 20. Similarly, thecasings or cylinders of metering devices 12-14 are provided with outletsfor respective connection to outlet conduits 21, 22 and 23. The outlet38 is angularly spaced from the inlet 37, say 90.

A cylindrical, plug-like valve member 40 is seated in the lower interiorregion of cylinder 31, being axially rotatable therein, and providedwith a coaxial shaft 41 extending downward rotatably through the bearing32 and upper wall of base 30 to the interior thereof. The valve member40 is formed interiorly of the cylinder 31 with a diametral through holeor passageway 42 located generally in the plane of inlet 37 and outlet38. Further, the valve member 40 is rotatable in the cylinder 31 todispose the passageway 42 in fluid communication with one of the inletand outlet 37 and 38, and is swingable or rotatable to dispose thepassageway in communication with the other of the outlets. At a locationangularly displaced from the diametral passageway 42, the valve member40 is formed with a peripheral cutout or port 43 which extends generallyvertically from the horizontal level of the inlet and outlet 37 and 38,upward through the upper side of the valve member. In addition, thevalve member 40 is formed centrally with a coaxial bore 44 extendingvertically upward from the mid-region of passageway 42 through the upperside of the valve member. It will now be appreciated that the valvemember 40 is shiftable between angularly spaced positions, being 90 inthe illustrated embodiment,

generally designated 10, and includes a plurality of separate whereinthe passageway 42 is shiftable between communicafluid metering devices11, 12, 13 and 14, each being connected to a respective source of fluidsupply, as by respective conduits 15, 16, 17 and 18. The severalmetering devices 11, 12, 13 and 14 are additionally connected in fluidcommunication through respective conduits 20, 21, 22 and 23, which thepassageway 42 communicates with inlet 37, as seen in the position ofFIG. 5.

An upper end member or plug-like stop is generally designated 46 anddisposed conformably rotatably within an upper region of the cylinder31. The upper end member or stop 46 may be provided with a sealing ring47 or other suitable sealing means in sealing engagement between thestop member 46 and cylinder 31. A coaxial externally threaded extensionor shaft 48 projects upwardly from the stop member 46 in threadedengagement through the upper end member or closure 33, and may beprovided with a manually actuable handle or rod 49. By this means, theposition of the stop member 46 is selectively adjustable verticallyrelative to the cylinder 31.

Depending coaxially from the stop member 46 is a hollow tubularextension or shaft 50 which engages slidably and conformably in thevertically opening bore 44 of valve member 40. Suitable sealing means,such as a sealing ring 53 may be interposed in sealing relation in thebore 44 between the surface thereof and the hollow tubular extension 50.The hollow shaft or tube 50 has its lower end open for permanentcommunication therethrough with the interior of bore 44 and consequentlywith passageway 42. In addition, the upper end of the hollow tube 50opens laterally, as at 51 from the stop member 46 into the upperinterior region of the cylinder 31.

A lower end stop member or spacer tube 52 is circumposed about thehollow shaft or tube 50 at the lower end thereof, resting on the uppersurface of valve member 40. Additionally, a piston 54 is freelyreciprocable in the cylinder 31, being rotatably circumposed about thehollow tube 50 and movable vertically between upper and lower positionsin abutting engagement with the upper stop member 46 and lower stopmember 52, respectively. The piston 54 may also be provided withsuitable sealing means 55 in sealing relation between the piston andcylinder 31. Further, the piston is provided with at least a ferrousmetal portion, say a ring 56 of magnetic material. Advantageously theremainder of the structure will be non-magnetic in character.

Externally of the cylinder 31 of metering unit 11, at vertically spacedlocations, are a pair of upper and lower piston sensing devices, such asproximity switches 57 and 58. These switches may be suitably mounted inspaced relation, as on a standard 59 fixed to the base 30, the switchesbeing vertically adjustable on the standard. The proximity switches 57and 58 are respectively responsive to movement of the piston with itsmagnetic part 56 upward and downward. In the illustrated embodiment, aswill appear more fully hereinafter, the upper and lower proximityswitches 57 and 58 are alternately closed upon movement of the piston 54to its upper limiting position and to its downward limiting position,the latter being shown in phantom in FIG. 2. Similarly, the severalmetering units 12, 13 and 14 are provided with upper and lower limitswitches, such as proximity switches, the metering device 12 havingupper and lower proximity switches 61 and 62, while the metering device13 includes upper and lower proximity switches 63 and 64, and themetering device 14 includes upper and lower proximity switches 65 and66. The proximity switches 61-66 of the metering units 12-14 all operatein a manner similar to the first described proximity switches 57 and 58,say to close upon movement of the associated piston into proximity withthe respective switch.

The additional metering devices 12, 13 and 14 each include in its lowerregion a plug-like axially rotatable valve member, substantiallyidentical to the valve member 40, and respectively designated 69, 70 and71, The valve members 69, 70 and 71 cooperate with their respectivecylinder inlets and outlets in substantially the same manner as thefirst described valve member 40, and are each further formed with acoaxial depending shaft, as at 72, 73 and 74, respectively, which mayeach be identical to the shaft 41 of valve member 40.

The shafts 41 and 72-74 depend rotatably from their respective valvemembers 40 and 69-71, into the hollow base 30. A generally horizontallydisposed, double ended crank arm 75 is keyed to the depending valvemember shaft 41, while a plurality of crank arms 76, 77 and 78 are eachrespectively keyed to the depending valve member shafts 72, 73 and 74.The several crank arms 75-78 may all be in substantial parallelism, asillustrated in F IG. 3, and connected together by a single bar or link80 extending in spaced parallelism with a plane extending through theaxes of shafts 41 and 72-74, and respectively pivotally connected to thecrank arms 75-78 by pivots 81, 82, 83 and 84. Thus, the several valvemembers 40 are positively connected together for simultaneous,equiangular rotation about their respective axes. As best seen in FIG.4. the several valve members 40 and 69-71 are all in angular alignmentwith each other, so that their operation in their respective cylindersis all identical at the same time. For example, in the illustratedcondition the internal passageway of each valve member 40 and 69-71 isin alignment with its adjacent outlet, and the generally verticallyextending, peripherally located port of each valve member is located incommunication with the respective cylinder inlet. Upon shifting movementof the bar link 80, to swing the valve members 40 and 69-71 thelocations of their respective passageways and ports relative to thecylinder inlets and outlets is reversed, as indicated in FIG. 5.

In addition, an actuating cylinder 86 may be mounted in the base 30, asby a pivot 87 at one end of the cylinder. A piston 88 is reciprocable inthe cylinder 86 and provided with an externally extending piston rod 89having its distal end pivotally connected, as by a pin 90, to the crankarm 75 remote from the pivot pin 81. The cylinder 86 may be providedadjacent to opposite ends with respective ports or fluid passageways 91and 92, the alternate ingress of fluid through said passagewayseffecting reciprocation of the piston 88, and swinging of the severalcrank arms 75-78. The alternate position of arm 75 is shown in phantom,corresponding to the phantom position of the actuating piston 88.

An electrical schematic of FIG. 6 may be employed, wherein the severalupper sensing means or proximity switches 57, 61, 63 and 65 are allconnected in series, and between a pair of supply conductors or lines 93and 94 across a suitable voltage supply. The lower sensing or proximityswitches 58, 62, 64 and 66 are also connected in series with each other,and also connected across the supply lines 93 and 94, so as to beparallel with the series connected upper proximity switches. A solenoid95 is connected in series with the upper proximity switches 57, 61, 63and 65, while a solenoid 96 is connected in series with the lowerproximity switches 58, 62, 64 and 66.'Thus, the solenoid 95 will beenergized upon closure of all the upper proximity switches, while thesolenoid 96 will be energized upon closure of all the lower proximityswitches.

As seen in FIG. 7, being a pneumatic diagram, the cylinder 86 has itsconduits 91 and 92 connected to a reversing valve 97 which is shiftedbetween its opposite positions by the solenoids 95 and 96. The reversingvalve is, in turn, connected to a source of pressurized fluid, as by asupply conduit 98, and to a low pressure or exhaust conduit 99. Uponalternate energization of solenoids 95 and 96, the cylinder conduits 91and 92 are alternately connected in fluid communication with the supplyconduit 98 and exhaust conduit 99 to effect repeated reciprocation ofthe piston 88 in cylinder 86.

In overall operation, as shown in the position of FIGS. 1-4, the singlepump 25 effectively reduces the fluid pressure at the outlets 20-23relative to the inlet conduits 15-18. If desired, the inlet conduits1548 may afford gravity feed, or additional pumps may be provided ifdesired.

By the pressure differential of the inlet fluids over the outlet fluids,the inlet fluids enter through the port 43 of valve member 40, and thecorresponding ports of respective valve members 69-71, to pass into therespective metering devices 11-14 beneath the pistons thereof. Theseveral pistons of the metering devices 11-14 are thereby moved upwardto a limiting position in abutting engagement with the correspondingupper end stop member, as at 46 in metering device 11, to

energize or close the several upper end proximity switches 57, 61, 63and 65. This action, as described, serves to discharge fluid from withineach of the cylinders of units 11-14 above the respective pistonsdownwardly through the associated hollow tubes, such as designated 50,and thence outward through the passageway of the valve members 40 and69-71.

Upon closure of the several upper end proximity switches 57, 61, 63 and65, the solenoid 95 is energized to effect reversal of valve 97 to shiftthe piston 88 to its opposite extreme position. This effects pivotalmovement of the several valve members 40 and 69-71 from the positionshown in FIG. 4 to that illustrated in FIG. 5.

Thereupon, the pressure differential against the inlet conduits 15-18 iscommunicated through the internal diametral passageway of each valvemember 40 and 69-71, upward through the hollow tube thereof into therespective cylinder on the upper side of the associated piston to shiftthe pistons downward. This downward movement of the piston 54, andcorresponding pistons of metering units 12-14 effects discharge of fluidfrom below the pistons outwardly through the port 43 and correspondingports of the valve members 69-71 to the outlet conduits -23. Uponmovement of the piston 54 and corresponding pistons of the remainingmetering devices to their lowermost limiting position, say in abutmentwith the stop sleeve 52 and corresponding stop members, the severalpistons effect closure of the lower end proximity switches 58, 62, 64and 66, the upper end limit switches, of course, have been opened upondownward movement of the pistons. The solenoid 96 is thereby energizedto operate the reversing valve 97 and effect return of the pneumaticsystem of FIG. 7 to its original condition, for repetition of theabove-described cycle of operation.

From the foregoing, it will now be appreciated that the fluidproportioning or continuous blending system of the instant inventionprovides a highly sanitary construction for use in the food and drugindustries, permitting of quick and easy disassembly and reassembly forcleaning or replacement of parts, is extremely simple and economical inconstruction and operation, requiring only a single pump regardless ofthe number of fluids being handled, permits of a great range ofvolumetric adjustmentby replacement or substitution of the stop sleevesor spacers 52, and further permits of fine volumetric adjustment, evenduring operation, by rotation of threaded stem 48 to vertically adjustthe position of upper end stop member 46.

Although the present invention has been described in some detail by wayof illustration and example for purposes of clarity of understanding, itis understood that certain changes and modifications may be made withinthe spirit of the invention.

What is claimed is:

l. A fluid proportioning system comprising a plurality of cylinders, aplurality of fluid inlets each opening into a respective cylinder andadapted for connection in fluid communication with a respective fluidsource, a piston in each cylinder and reciprocable therein betweenopposite limiting positions, a plurality of fluid outlets each openingfrom a respective cylinder for communication with a common vessel, valvemeans in each cylinder selectively positionable to communicate theassociated inlet to a selected side of the associated piston andcommunicate the associated outlet to the other piston side, operatingmeans interconnecting said valve means for simultaneous shifting thereofbetween selected positions, and actuating means for actuating saidoperating means only upon completion of the strokes of all of saidpistons, whereby the frequency of reciprocation of all the pistons isequal, said pistons being freely reciprocable in respective cylindersindependently of each other, for separate and independent pistonreciprocation responsive to pressure differential between inlet andoutlet fluids, and selectively positionable limit means in each cylinderfor independently limiting piston movement to selected positions.

2. A fluid proportioning system comprising a plurality of cylinders, aplurality of fluid inlets each opening into a respective cylinder andadapted for connection in fluid communication with a respective fluidsource, a piston in each cylinder and reciprocable therein betweenopposite limiting positions, a plurality of fluid outlets each openingfrom a respective cylinder for communication with a common vessel, valvemeans in each cylinder selectively positionable to communicate theassociated inlet to a selected side of the associated piston andcommunicate the associated outlet to the other piston side, operatingmeans interconnecting said valve means for simultaneous shifting thereofbetween selected positions, and actuating means for actuating saidoperating means only upon completion of the strokes of all of saidpistons, whereby the frequency of reciprocation of all the pistons isequal, said pistons being freely reciprocable in respective cylinders,for piston reciprocation responsive to pressure differential betweeninlet and outlet fluids, said valve means each comprising a rotary valvemember located on one side of the associated piston having an internalpassageway communicating in all positions of rotative movement with theother side of the associated piston, said passageway being rotatablewith said valve member to communicate selectively with said inlet andoutlet, and a port in said valve member communicating in all positionsof rotative movement with said one side of the associated piston androtative with said valve member to communicate with the outlet when saidpassageway communicates with the inlet and to communicate withthe inletwhen said passageway communicates with the outlet, said operating meanscomprising a shaft extending from each rotary member, and crank meanspositively connecting said shafts for simultaneous rotation of saidrotary members, said actuating means comprising a first group of seriesconnected switches associated with respective pistons at one limitingposition thereof, and a second group of series connected switchesassociated with respective pistons at the opposite limiting positionthereof, said groups being connected in parallel with each other foralternate actuation of said valve operating means upon repeatedreciprocation of said pistons.

3. A fluid proportioning system comprising a plurality of cylinders, aplurality of fluid inlets each opening into a respective cylinder andadapted for connection in fluid communication with a respective fluidsource, a piston in each cylinder and reciprocable therein betweenopposite limiting positions, a plurality of fluid outlets each openingfrom a respective cylinder for communication with a common vessel, valvemeans in each cylinder selectively positionable to communicate theassociated inlet to a selected side of the associated piston andcommunicate the associated outlet to the other piston side, operatingmeans interconnecting said valve means for simultaneous shifting thereofbetween selected positions, and actuating means for actuating saidoperating means only upon completion of the strokes of all of saidpistons, whereby the frequency of reciprocation of all the pistons isequal, said actuating means comprising a first group of series connectedswitches associated with respective pistons at one limiting positionthereof, and a second group of series connected switches associated withthe respective pistons at the opposite limiting position thereof, saidgroups being connected in parallel with each other for alternateactuation of said valve operating means upon repeated reciprocation ofsaid pistons.

4. A fluid proportioning system according to claim 3, said valve meanseach comprising a rotary valve member located on one side of theassociated piston having an internal passageway communicating in allpositions of rotative movement with the other side of the associatedpiston, said passageway being rotatable with said valve member tocommunicate selectively with the inlet and outlet, and a port in saidvalve member communicating in all positions of rotative movement withsaid one side of the associated piston and rotative with said valvemember to communicate with the outlet when said passageway communicateswith the inlet and to communicate with the inlet when said passagewaycommunicates with the outlet.

5. A fluid proportioning system according to claim 4, said operatingmeans comprising a shaft extending from each rotary member, and crankmeans positively connecting said shafts for simultaneous rotation ofsaid rotary members.

1. A fluid proportioning system comprising a plurality of cylinders, aplurality of fluid inlets each opening into a respective cylinder andadapted for connection in fluid communication with a respective fluidsource, a piston in each cylinder and reciprocable therein betweenopposite limiting positions, a plurality of fluid outlets each openingfrom a respective cylinder for communication with a common vessel, valvemeans in each cylinder selectively positionable to communicate theassociated inlet to a selected side of the associated piston andcommunicate the associated outlet to the other piston side, operatingmeans interconnecting said valve means for simultaneous shifting thereofbetween selected positions, and actuating means for actuating saidoperating means only upon completion of the strokes of all of saidpistons, whereby the frequency of reciprocation of all the pistons isequal, said pistons being freely reciprocable in respective cylindersindependently of each other, for separate and independent pistonreciprocation responsive to pressure differential between inlet andoutlet fluids, and selectively positionable limit means in each cylinderfor independently limiting piston movement to selected positions.
 2. Afluid proportioning system comprising a plurality of cylinders, aplurality of fluid inlets each opening into a respective cylinder andadapted for connection in fluid communication with a respective fluidsource, a piston in each cylinder and reciprocable therein betweenopposite limiting positions, a plurality of fluid outlets each openingfrom a respective cylinder for communication with a common vessel, valvemeans in each cylinder selectively positionable to communicate theassociated inlet to a selected side of the associated piston andcommunicate the associated outlet to the other piston side, operatingmeans interconnecting said valve means for simultaneous shifting thereofbetween selected positions, and actuating means for actuating saidoperating means only upon completion of the strokes of all of saidpistons, whereby the frequency of reciprocation of all the pistons isequal, said pistons being freely reciprocable in respective cylinders,for piston reciprocation responsive to pressure differential betweeninlet and outlet fluids, said valve means each comprising a rotary valvemember located on one side of the associated piston having an internalpassageway communicating in all positions of rotative movement with theother side of the associated piston, said passageway being rotatablewith said valve member to communicate selectively with said inlet andoutlet, and a port in said valve member communicating in all positionsof rotative movement with said one side of the associated piston androtative with said valve member to communicate with the outlet when saidpassageway communicates with the inlet and to communicate with the inletwhen said passageway communicates with the outlet, said operating meanscomprising a shaft extending from each rotary member, and crank meanspositively connecting said shafts for simultaneous rotation of saidrotary members, said actuating means comprising a first group of seriesconnected switches associated with respective pistons at one limitingposition thereof, and a second group of series connected switchesassociated with respective pistons at the opposite limiting positionthereof, said groups being connected in parallel with each other foralternate actuation of said valve operating means upon repeatedreciprocation of said pistons.
 3. A fluid proportioning systemcomprising a plurality of cylinders, a plurality of fluid inlets eacHopening into a respective cylinder and adapted for connection in fluidcommunication with a respective fluid source, a piston in each cylinderand reciprocable therein between opposite limiting positions, aplurality of fluid outlets each opening from a respective cylinder forcommunication with a common vessel, valve means in each cylinderselectively positionable to communicate the associated inlet to aselected side of the associated piston and communicate the associatedoutlet to the other piston side, operating means interconnecting saidvalve means for simultaneous shifting thereof between selectedpositions, and actuating means for actuating said operating means onlyupon completion of the strokes of all of said pistons, whereby thefrequency of reciprocation of all the pistons is equal, said actuatingmeans comprising a first group of series connected switches associatedwith respective pistons at one limiting position thereof, and a secondgroup of series connected switches associated with the respectivepistons at the opposite limiting position thereof, said groups beingconnected in parallel with each other for alternate actuation of saidvalve operating means upon repeated reciprocation of said pistons.
 4. Afluid proportioning system according to claim 3, said valve means eachcomprising a rotary valve member located on one side of the associatedpiston having an internal passageway communicating in all positions ofrotative movement with the other side of the associated piston, saidpassageway being rotatable with said valve member to communicateselectively with the inlet and outlet, and a port in said valve membercommunicating in all positions of rotative movement with said one sideof the associated piston and rotative with said valve member tocommunicate with the outlet when said passageway communicates with theinlet and to communicate with the inlet when said passagewaycommunicates with the outlet.
 5. A fluid proportioning system accordingto claim 4, said operating means comprising a shaft extending from eachrotary member, and crank means positively connecting said shafts forsimultaneous rotation of said rotary members.